Omron DEVICENET Operation Manual page 104

Minimizing Noise in the Network
Network with 1 Communications Power Supply
Power Supply Tap,
T-branch Tap, or
T-branch Connector
Master
PS
Ferrite Core (Data Line Filter):
Nisshin Electric Co, Ltd. model 0443-164151 or equivalent
Inductance specifications
25 MHz
156 Ω
30 mm
13 mm
• Since noise currents often flow through metallic equipment (such as cas-
ings), the communications cables should be placed as far away from
metallic equipment as possible.
• Ground the communications cable to 100 Ω max. with a ground wire that
is as short as possible.
• Ground the shielding wire on the communications cable at one point. If
the same ground is used for the communications cable and communica-
tions power supply, there is a possibility that noise may be transmitted
through the ground line to the communications line. In order to avoid this,
be sure that the power line ground and the grounds for the communica-
tions cables and the communications power supply are located as far
from each other as possible.
• Insert a line filter on the primary side of the communications power sup-
ply.
• When there are two or more communications power supplies, ground the
shielding wire at the Power Supply Tap near the center of the communica-
tions cable. Do not ground the shielding wire at more than one place.
(In the following diagram, "PS" indicates a communications power supply.)
Master
Slave
Note Do not connect the Power Supply Tap's shield (S) terminal to the communica-
tions power supply's FG terminal at these two Power Supply Taps.
100 MHz
250 Ω
32 mm
29 mm
Network with 2 or more Communications Power Supplies
Power
Supply Taps
(See note.)
Slave
PS PS
Section 2-5
Ground at
Power
one point
Supply Tap
(See note.)
Slave
PS
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